1. Field of the Invention
The present invention relates to a power wrench for a machine tool drawbar.
2. Description of the Prior Art
A collet release mechanism for machine tools is shown in U.S. Pat. No. 4,511,295 which includes a pneumatic motor having a drive shaft that rotates a socket type wrench, and which is vertically slid up and down on guide posts by use of a pneumatic cylinder that is operated by movement of a control valve by an operator.
The operation using a valve and pneumatic cylinder is complicated, and does not give the operator any sense of movement as to whether the operator is tightening or loosening the drawbar. The operator has to make sure that the right valve button is pushed for operation.
Another type of pneumatically operated spindle wrench as shown in U.S. Pat. No. 4,382,730, which uses a standard wrench with a operate handle that operates directly against the switch on a pneumatic motor that is part of a normal pneumatic wrench. This device requires swinging the motor into position over the drawbar.
Various other power operated drawbars are advanced, but none which are simple, mechanically controlled attachments that can go onto an existing machine tool, such as a milling machine, or build in, and provide manual operation and also provide the sense of direction by rotating the actuator in opposite directions for locking (tightening) or unlocking (loosening) the drawbar.
For example, U.S. Pat. No. 3,481,248 shows a drawbar that has a power motor directly installed, as does U.S. Pat. No. 3,898,911. Additionally, the other patents that were cited in U.S. Pat. No. 4,511,295 illustrate the state-of-the-art.